Numerous open-loop current sensors exist comprising a magnetic circuit having an air-gap and a Hall cell disposed in the air-gap for measuring the magnetic field induced by an electric current flowing along a conductor passing through the magnetic circuit. The magnetic circuit is typically made of a material that conducts magnetic flux, i.e. a “magnetic material”, and that is laminate. The Hall cell can have electrical terminals in the form of pins mounted orthogonally on a printed circuit.
Conventional open-loop sensors of the above-mentioned type are relatively costly to manufacture due to the cost of manufacturing laminate magnetic circuits and due to cost of assembling the various components, in particular the Hall cell and the magnetic circuit in a housing, while complying with the dimensions and the tolerances of the air-gap and with the position of the Hall cell for guaranteeing good measurement accuracy.
Another problem with conventional open-loop current sensors is that they are not robust enough for certain uses, e.g. for use in the automobile field in which components must be capable of withstanding impacts and vibration without losing measurement accuracy. In certain uses, in which the current sensor must be resistant to the environment and airtight, the magnetic circuit and the Hall cell are covered with a resin. However, that can have detrimental consequences on measurement accuracy because of the different coefficients of expansion, in particular the different thermal and/or humidity coefficients of expansion, of the magnetic circuit, of the resin, and/or of the housing, giving rise to mechanical stresses being exerted on the magnetic circuit. Variation in the air-gap due to such stresses gives rise to errors in measuring the magnetic induction and thus in measuring the electric current.